WAREHAM, Mass. -- After parking her truck in this beachside town in July, local resident Pamela Miller says she was confronted by a man wearing a neon-lemon "Parking Enforcement" T-shirt. He accused her of parking illegally, called her "retarded," and, after she refused to move her truck, bumped her legs with his Ford Crown Victoria, she later told town officials.

With the economic downturn, there's been a fresh boom across the country in volunteer cadres of citizens taking on some of the routine duties...